There exist a number of PV/T hybrid solar collector systems using PV/T modules to convert solar energy into electrical energy. The efficiency of the solar cells or photovoltaic cells keeps improving whereas costs continue to reduce, thus making solar energy an important and viable source of renewable and environment friendly energy.
Conventional PV/T modules are manufactured by encapsulating solar cells, which are very brittle, in a laminate structure to protect them from optical and mechanical damage due to continuous exposure to sunlight and the weather elements. Additionally, PV/T modules comprise a cooling/absorbing element containing fluid for carrying away the heat accumulated in the solar cells which affects the performance of the solar cell. However, in order to reach efficiency in a PV/T hybrid solar collector it is necessary to reach a certain minimum temperature of the cooling/absorbent fluid whilst at the same time the voltage output of the photovoltaic cells decreases with increasing temperature. This dual functionality places strict requirements on the materials used in the PV/T module.
Examples of such PV/T modules are disclosed in EP 2 405 489, DE 198 09 883 and WO 2011/146029, which are incorporated herein by reference. These known PV/T modules are typically manufactured with laminate layers of polymer films comprising e.g. ethylene vinyl acetate (EVA), fluoropolymers such as polyvinyl fluoride (PVF) or polyvinyl butyral (PVB) and/or silicone polymers. The polymer films are cut and placed such that the solar cells are sandwiched between two polymer layers of EVA, PVF and/or PVB and subsequently the layers are laminated together in vacuum at an appropriate temperature. The laminated solar cell structure is then afterwards integrated with the cooling/absorbing element in the form of a heat transfer plate or heat exchanger having tubes for passage of a cooling fluid.
However, because of the considerable temperature gradients across the PV/T module, especially in coolers having fluid channels interspaced by flanges such as DE 198 09 883 and WO 2011/146029, the thermal expansion experienced by the cooler and the solar cells varies and may cause damage to the solar cells and the laminate layers made from polymer films, such as deformation, cracking, delamination, separation from the cooling element etc. and also limit the efficiency of the solar cells.
Hence, there is a need to develop improved PV/T modules and manufacturing methods therefor.